In the past, optically active alpha-tocooherol and derivatives thereof which are the 2R,4'R,8'R is isomers of compounds of the formula: ##STR1## have been prepared through insulation from natural sources such as vegetable oil. This procedure suffers from many drawbacks due to the fact that the tocopherol content of these oils is very small. Therefore, a great amount of oil must be processed in order to isolate a small amount of natural tocopherol. Additionally, the process whereby various tocopherols are isolated from vegetable oil is extremely cumbersome.
In U.S. Pat. application Ser. No. 417,465, filed Nov. 19, 1973, Scott et al., vitamin E active compounds have been synthesized by utilizing a compound of the formula: ##STR2## wherein R forms with its attached oxygen moiety an ether protecting group removable by hydrogenolysis or acid catalyzed cleavage; and R' is lower alkyl;
And a compound of the formula: ##STR3## The compound of formula II can be a racemate of 2R or 2S isomer, depending upon the desired isomeric form of the compound of formula I. (Please note, the compound of the formula VII in U.S. Pat. application Ser. No. 417,465, filed Nov. 19, 1973).
The compound of formula III can also be a racemate or various 2 and 6, R and S isomers. (Please note compound XLIV in U.S. Pat. application Ser. No. 417,465, filed Nov. 19, 1973). Where the compound of the formula III has a 2R, 6R configuration, i.e., a compound of the formula: ##STR4## then natural .alpha. -tocopherol is produced when the compound of the formula III-A and the 2S isomer of the compound of formula II are utilized.
In accordance with this process, it has been desired to provide a simple and economic method for preparing the compound of formula III and III-A, natural vitamin E and isomers derived therefrom from relatively cheap and economic starting materials.